1. Field of the Invention
The present invention relates to stable, concentrated, low-viscosity solutions of direct dyes. More specifically, the invention relates to high strength liquid dyes wherein the dye is formed by diazotizing 4'-aminoazobenzene-4-sulfonic acid and coupling into J-Acid.
2. Description of the Prior Art
Liquid dyes are commercially important for dyeing papers, textile goods, carpet structures and other materials such as glass fibers. These liquid dyes may be direct, acid, and basic dyes and are ideally completely dissolved in water in high strength. High strength means that the liquid dye is 25%-50% the strength of the corresponding commercial powder version of the dye. Commercial dyes usually range from about 20% to 60% pure dye, the balance being processing salts or dyeing adjuvants. Thus, the amount of pure dye in a high strength liquid dye will be in the range 5% to 30% pure dye.
The prior art discloses various means for achieving the desired solubility and strength of liquid dyes. These include the use of organic solvents, selected cations, metallization aids and the like. Among the organic solvents and aids disclosed for liquid dyes are dimethylsulfoxide (U.S. Pat. No. 3,551,088); glycols and glycol ethers, amides, butyrolactone, acetonitrile, tetrahydrofuran, dioxane, dimethylsulfoxide, and N-methylpyrrolidene (U.S. Pat. No. 3,346,322). Acid amides (preferably urea) are disclosed in British Pat. No. 1,202,798 and U.S. Pat. No. 4,023,924; hydroxyethylated quaternized alkyl amines, isopropyl alcohol, butyl alcohol, ethyl alcohol, formamide and dimethylformamide in U.S. Pat. No. 3,995,997; .epsilon.-caprolactam/polyalcohol association compounds in U.S. Pat. No. 3,963,430; monopropanolamine, 1-amino-2-hydroxypropane and aminothiole in U.S. Pat. No. 3,700,653; and tertiary amines in U.S. Pat. No. 3,852,029. Diethanolamine is disclosed as a metallization aid and a solvent in U.S. Pat. No. 3,829,287 and triethanolamine is used as an acid acceptor in U.S. Pat. No. 3,681,320.
Despite the extensive prior art relating to liquid dyes, a need still exists for specific applications for more highly concentrated dyes having an optimum balance of properties such as a low ratio of organic compound (i.e., organic solvent, solubilizing aid, etc.) to dye (because of ecological reasons), low viscosity and increased stability.
It is an object according to the present invention, therefore, to provide concentrated liquid dye solutions wherein the dye, in free acid form, has the formula (I): ##STR2##
It is a further object to provide the concentrated liquid dyes as defined above and having superior stability while maintaining a low viscosity.
A liquid dye of the above structure is disclosed by Conger, Sr., U.S. Pat. No. 4,019,858. However, the Conger, Sr., liquid contains 15-16% of the organic solvent, urea, at 29-31% strength (Conger, Sr.; Example 1).